Rapid linear scale-up of a protein separation by centrifugal partition chromatography

Nonlinear liquid-liquid chromatography: Modeling a binary mixture separation

In liquid-liquid chromatography (LLC), mixture components are separated due to their different distribution between the phases of a biphasic liquid system composed of three or four solvents. LLC separations are typically modeled assuming that only the solutes distribute between the two liquid phases and their distribution can be described with a concentration-independent distribution constant. With increasing solute concentration, the physicochemical properties of the biphasic system change, and the distribution of the solutes becomes a function of their concentration. However, the experimental determination of liquid-liquid equilibria in multicomponent systems is time-intensive, and its prediction using thermodynamic models is often not sufficiently accurate for process design purposes. Thus, in this work, we propose a simple approach to model and simulate LLC separations in the nonlinear (concentration-dependent) range of the solutes' distribution equilibria, namely cannabidiol (CBD) and cannabigerol (CBG). Using the inverse method, the distribution equilibrium equation parameters were estimated from pulse injection experiments of single solutes at concentrations ranging from 1 to 100 mg/mL and 1-50 mg/mL for CBD and CBG, respectively. The obtained parameters were then successfully used to predict the elution profiles of binary mixtures of different compositions at 40 mg/mL total cannabinoid concentration. The approach was demonstrated and validated for CBD and CBG as model compounds and n-hexane/methanol/water 10/7.5/2.5 (v/v/v) as the biphasic solvent system. It should be noted that the applicability of the proposed approach is system-dependent, and hence, it should be evaluated for each separation task individually.

Scale-up of Aflatoxin Purification by Centrifugal Partition Chromatography

Aflatoxins (AFs) are a group of secondary metabolites that cause several diseases in both animals and humans. Since the discovery of this group of toxins, several effects were revealed, such as hepatic changes, carcinoma, failure, and cancer of the liver. In the European Union, there are concentration limits for this group of mycotoxins in food and feed products; thus, these substances are required in their pure forms to prepare reference standards or certified reference materials. In our present work, a liquid–liquid chromatographic method utilizing a toluene/acetic acid/water ternary system was improved. In order to enhance the purification and gain a higher amount of pure AFs in one separation run, a scale-up of the previous separation was carried out. In several scale-up steps—including the determination of the maximum concentration and volume to load on a 250 mL rotor via a loop and via a pump as well, and the quadruplication of the entire separation procedure to a 1000 mL rotor—an efficient scale-up was achieved. Utilizing a 250 mL rotor in an 8-hour workday, altogether approximately 2.2 g of total AFs could be purified with 8.2 liters of solvent, while on a 1000 mL column, approximately 7.8 g AFs could be prepared, utilizing around 31 liters of solvents.

Development of Centrifugal Partition Chromatography for the Purification of Antibody-Drug Conjugates

Monoclonal antibody-drug conjugates (ADCs) are an expanding therapeutic class of biomolecules for which relatively few analytical and preparative separation options exist. Purification of ADCs with a specific drug antibody ratio is even more challenging. We report the first application of countercurrent separation (CCS) to this problem. An ADC mimic was successfully chromatographed using an aqueous two-phase system (ATPS) consisting of PEG 1000/sodium citrate pH 7.5/water, 17.75/17.75/64.50 (w/w/w). Notably, different partition coefficients (K) in this ATPS for the ADC mimic (0.09 < K < 0.16) and its monoclonal antibody backbone, IgG (0.16 < K < 0.27), were observed using CCS. Differential elution behavior of such high-molecular-weight biomolecules, 146,441 vs. ∼150,000 Da, using CCS has no precedent. The results provide a proof of concept for further exploration of the application of ATPSs and CCS to the separation of ADCs.

Liquid-Liquid Chromatography: Current Design Approaches and Future Pathways

Since its first appearance in the 1960s, solid support-free liquid-liquid chromatography has played an ever-growing role in the field of natural products research. The use of the two phases of a liquid biphasic system, the mobile and stationary phases, renders the technique highly versatile and adaptable to a wide spectrum of target molecules, from hydrophobic to highly polar small molecules to proteins. Generally considered a niche technique used only for small-scale preparative separations, liquid-liquid chromatography currently lags far behind conventional liquid-solid chromatography and liquid-liquid extraction in process modeling and industrial acceptance. This review aims to expose a broader audience to this high-potential separation technique by presenting the wide variety of available operating modes and solvent systems as well as structured, model-based design approaches. Topics currently offering opportunities for further investigation are also addressed.

Recent progress in separation prediction of counter-current chromatography

As a liquid-liquid partition chromatography, counter-current chromatography has advantages in large sample loading capacity without irreversible adsorption, which has been widely applied in separation and purification fields. The main factors, including partition coefficient, two-phase solvent systems, apparatus, and operating parameters greatly affect the separation process of counter-current chromatography. To promote the applications of counter-current chromatography, it is essential to develop theoretical research to master the principles of counter-current chromatographic separations so as to achieve predictions before laborious trials. In this article, recent progress about separation prediction methods are reviewed from a point of the steady and unsteady state of the mass transfer process of counter-current chromatography and its mass transfer characteristics, and then it is divided into three aspects: prediction of partition coefficient, modeling the thermodynamic process of counter-current chromatography, and modeling the dynamic process of counter-current chromatography.

Evaluation of Inter-Apparatus Separation Method Transferability in Countercurrent Chromatography and Centrifugal Partition Chromatography

In the countercurrent chromatography and centrifugal partition chromatography, separation method transfer and scale-up is often described as an easy and straightforward procedure. Separation methods are usually developed on lab scale columns and subsequently transferred using linear scale-up factors to semi-preparative or preparative columns of the same column design. However, the separation methods described in the literature have been developed on various columns of different design and size. This is accompanied by differences in the separation behavior of the columns and therefore makes separation method transfer difficult. In the current study, the separation performances of different columns were evaluated and compared. Linear correlations of stationary phase retention and column efficiency as a function of flow rate were found to be applicable for the calculation of separation resolution in the typical operating range of each column. In this context, a two-point short-cut approach for a fast column characterization is recommended. This allows a quick prediction of the separation method transferability between columns, which saves experimental time and effort. In the current study, the transferability between five different columns from lab scale countercurrent chromatography (CCC) (18 mL) to semi-preparative centrifugal partition chromatography (CPCs) (250 mL) with different cell numbers and design is investigated.

Mass Transfer of Proteins in Aqueous Two-Phase Systems

Aqueous Two-Phase Extraction is known to be a gentle separation technique for biochemical molecules where product partitioning is fast. However, the reason for the high mass transfer rates has not been investigated, yet. Many researchers claim that the low interfacial tension facilitates the formation of very small droplets and with it a large interfacial area causing a fast partitioning. However, an experimental evidence for this hypothesis has not been published yet. In this study, the mass transfer coefficients of two proteins, namely lysozyme and bromelain, were determined by providing a defined interfacial area for partitioning. Compared to low molecular weight solutes the mass transfer coefficient for the proteins investigated was small proving for the first time that the large interfacial area and not fast diffusion seems to be the reason for fast protein partitioning.

Continuous Synthesis and Purification by Coupling a Multistep Flow Reaction with Centrifugal Partition Chromatography

Continuous-flow multistep synthesis is combined with quasi-continuous final-product purification to produce pure products from crude reaction mixtures. In the nucleophilic aromatic substitution of 2,4-difluoronitrobenzene with morpholine followed by a heterogeneous catalytic hydrogenation, the desired monosubstituted product can be continuously separated from the co- and by-products in a purity of over 99 % by coupling a flow reactor sequence to a multiple dual-mode (MDM) centrifugal partition chromatography (CPC) device. This purification technique has many advantages over HPLC, such as higher resolution and no need for column replacement or silica recycling, and it does not suffer from irreversible adsorption.

Centrifugal partition chromatography in a biorefinery context: Optimisation and scale-up of monosaccharide fractionation from hydrolysed sugar beet pulp

The isolation of component sugars from biomass represents an important step in the bioprocessing of sustainable feedstocks such as sugar beet pulp. Centrifugal partition chromatography (CPC) is used here, as an alternative to multiple resin chromatography steps, to fractionate component monosaccharides from crude hydrolysed sugar beet pulp pectin. CPC separation of samples, prepared in the stationary phase, was carried out using an ethanol: ammonium sulphate (300gL^-1) phase system (0.8:1.8v:v) in ascending mode. This enabled removal of crude feedstream impurities and separation of monosaccharides into three fractions (l-rhamnose, l-arabinose and d-galactose, and d-galacturonic acid) in a single step. Throughput was improved three-fold by increasing sample injection volume, from 4 to 16% of column volume, with similar separation performance maintained in all cases. Extrusion of the final galacturonic acid fraction increased the eluted solute concentration, reduced the total separation time by 24% and removed the need for further column regeneration. Reproducibility of the separation after extrusion was validated by using multiple stacked injections. Scale-up was performed linearly from a semi-preparative 250mL column to a preparative 950mL column with a scale-up ratio of 3.8 applied to mobile phase flow rate and sample injection volume. Throughputs of 9.4gL^-1h^-1 of total dissolved solids were achieved at the preparative scale with a throughput of 1.9gL^-1h^-1 of component monosaccharides. These results demonstrate the potential of CPC for both impurity removal and target fractionation within biorefinery separations.

One-step isolation of carnosic acid and carnosol from rosemary by centrifugal partition chromatography

Carnosic acid and carnosol are the main bioactive components responsible for the significant antioxidant activity of Rosmarinus officinalis. Nevertheless, they are known for their instability in solutions. Separation of both compounds from crude rosemary extract was successfully achieved by one-step centrifugal partition chromatography without any degradation. A two-phase solvent system, hexane/ethyl acetate/methanol/water (3:2:3:2 v/v) was run on a preparative scale applying the elution-extrusion technique in descending mode. A 900 mg quantity of the crude extract containing 39.7% carnosic acid and 12.3% carnosol was loaded onto a 500 mL column, rotating at 1800 rpm. Carnosic acid and carnosol were obtained at purities of 96.1 ± 1% and 94.4 ± 0.9%, with recoveries of 94.3 ± 4.4% and 94.8 ± 2.3%, respectively. The compounds were identified by mass spectrometry, tandem mass spectrometry, and comparison with authentic standards.

New analytical spiral tube assembly for separation of proteins by counter-current chromatography

A new spiral column assembly for analytical separation by counter-current chromatography is described. The column is made from a plastic spiral tube support which has 12 interwoven spiral grooves. The PTFE tubing of 1.6mm ID was first flattened by extruding through a narrow slit and inserted into the grooves to make 5 spiral layers with about 60ml capacity. The performance of the spiral column assembly was tested with separation of three stable protein samples including cytochrome C, myoglobin and lysozyme in a polymer phase system composed of polyethylene glycol 1000 and dibasic potassium phosphate each at 12.5% (w/w) in water. At 2ml/min, three protein samples were well resolved in 1h. The separation time may be further shortened by application of higher revolution speed and flow rate by improving the strength of the spiral tube support in the future.

Separation of active laccases from Pleurotus sapidus culture supernatant using aqueous two-phase systems in centrifugal partition chromatography

For the production of bio active compounds, e.g., active enzymes or antibodies, a conserved purification process with a minimum loss of active compounds is necessary. In centrifugal partition chromatography (CPC), the separation effect is based on the different distribution of the components to be separated between two immiscible liquid phases. Thereby, one liquid phase is kept stationary in chambers by a centrifugal field and the mobile phase is pumped through via connecting ducts. Aqueous two phase systems (ATPS) are known to provide benign conditions for biochemical products and seem to be promising when used in CPC for purification tasks. However, it is not known if active biochemical compounds can "survive" the conditions in a CPC where strong shear forces can occur due to the two-phasic flow under centrifugal forces. Therefore, this aspect has been faced within this study by the separation of active laccases from a fermentation broth of Pleurotus sapidus. After selecting a suitable ATPS and operating conditions, the activity yield was calculated and the preservation of the active enzymes could be observed. Therefore, CPC could be shown as potentially suitable for the purification of bio-active compounds.

Comparison of twin-cell centrifugal partition chromatographic columns with different cell volume

Two twin-cell centrifugal partition chromatographic columns (SCPC 250 and SCPE-250-BIO, Armen Instrument, France) with the same column volume but different cell size and number were compared in terms of stationary phase retention and column efficiency. The columns were tested with two types of solvent systems: a commonly used organic solvent based biphasic system from the ARIZONA solvent system family and a polymer/salt based aqueous two phase system (ATPS). The efficiency of the columns was evaluated by pulse injection experiments of two benzenediols (pyrocatechol and hydroquinone) in the case of the ARIZONA system and a protein mixture (myoglobin and lysozyme) in the case of the ATPS. As result of high stationary phase retention, the column with the lower number of larger twin-cells (SCPE-250-BIO) is suitable for protein separations using ATPS. On the other hand, due to higher column efficiency, the column with the greater number of smaller cells (SCPC 250) is superior for batch elution separations performed with standard liquid-liquid chromatography organic solvent based biphasic systems.

Study of the applicability of non-conventional aqueous two-phase systems in counter-current and centrifugal partition chromatography

Aqueous two-phase systems composed of imidazolium-based ionic liquids and phosphate salts were evaluated for their applicability in liquid-liquid chromatography. The influence of the nature of ionic liquid anion and cation on the partitioning of bovine serum albumin, lysozyme and myoglobin was investigated. A mixture of K2HPO4 and KH2PO4 in a ratio of 1.82:1 wt/wt was used in all of the tested biphasic systems to adjust the pH to a range of 7-8. The results show that more hydrophobic cations decrease the partition coefficients of the proteins in the biphasic systems and outweigh the effect of the anion on the distribution of the macromolecules. Viscosities and densities of the biphasic systems were in a suitable range for liquid-liquid chromatography. Even though the partition coefficients were too high for a conventional batch operation mode, these aqueous two-phase systems show favorable properties for protein capturing in liquid-liquid chromatographic columns. Additionally, the possible application of ionic liquids as modifiers in polyethylene glycol (PEG)-based aqueous two-phase systems was investigated. It could be demonstrated that ionic liquids alter the partition coefficients of the proteins.

Downstream processing of virus-like particles: single-stage and multi-stage aqueous two-phase extraction

The demand for vaccines against untreated diseases has enforced the research and development of virus-like particle (VLP) based vaccine candidates in recent years. Significant progress has been made in increasing VLP titres during upstream processing in bacteria, yeast and insect cells. Considering downstream processing, the separation of host cell impurities is predominantly achieved by time-intensive ultracentrifugation processes or numerous chromatography and filtration steps. In this work, we evaluate the potential of an alternative separation technology for VLPs: aqueous two-phase extraction (ATPE). The benefits of ATPE have been demonstrated for various biomolecules, but capacity and separation efficiency were observed to be low for large biomolecules such as VLPs or viruses. Both performance parameters were examined in detail in a case study on human B19 parvovirus-like particles derived from Spodoptera frugiperda Sf9 insect cells. A solubility-guided approach enabled the design of polyethylene (PEG) salt aqueous two-phase systems with a high capacity of up to 4.1mg/mL VLPs. Unique separation efficiencies were obtained by varying the molecular weight of PEG, the pH value and by using neutral salt additives. Further improvement of the separation of host cell impurities was achieved by multi-stage ATPE on a centrifugal partition chromatography (CPC) device in 500mL scale. While single-stage ATPE enabled a DNA clearance of 99.6%, multi-stage ATPE improved the separation of host cell proteins (HCPs). The HPLC purity ranged from 16.8% (100% VLP recovery) for the single-stage ATPE to 69.1% (40.1% VLP recovery) for the multi-stage ATPE. An alternative two-step downstream process is presented removing the ATPS forming polymer, cell debris and 99.77% DNA with a HPLC purity of 90.6% and a VLP recovery of 63.9%.

Phase system selection with fractional factorial design for purification of recombinant cyanovirin-N from a hydroponic culture medium using centrifugal partition chromatography

Centrifugal partition chromatography (CPC) with an aqueous two-phase system (ATPS) was used to purify recombinant cyanovirin-N (CV-N) from other proteins which were co-secreted into a hydroponic plant medium in a rhizosecretion process. To achieve satisfactory protein concentration, the purification was preceded by ultrafiltration performed on a 5 kDa filter. ATPS, because of their gentle nature, were selected as the phase system for CPC. A systematic phase system selection was applied. This involved studying the effect of seven parameters of ATPS: polymer type, salt type, the polymer and salt concentration, the polymer molecular weight, pH, and presence of two additional salts; NaCl and NaClO4, which all together gave 320 combinations. design of experiment (DoE) software allowed the reduction of this number to 46. Having tested partitioning of cyanovirin-N and impurities in 46 ATPS, the three best potential phase systems generated by the programme were then tested on the CPC. Out of these three, 13/13% PEG4000 sodium phosphate, pH 3.0, proved to be most effective phase system in the purification of cyanovirin-N, judged by ELISA and SDS-PAGE analysis, as it eliminated most of the impurities from the final cyanovirin-N preparation.

Green improved processes to extract bioactive phenolic compounds from brown macroalgae using Sargassum muticum as model

A comparative study between "alternative" extraction processes such as centrifugal partition extraction (CPE), supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE) and classical solid/liquid used in the laboratory are currently focusing on the efficiency (selectivity and productivity) to obtain bioactive phenolic compounds from the phaeophyte Sargassum muticum model. The choice of the best process was based on several measurements: (i) the total phenolic content measured by the colorimetric Folin-Ciocalteu assay, (ii) radical scavenger and antioxidant activities assessed by the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay, and the β-carotene bleaching method and finally (iii) the method productivity. Irrespective of the solvent used in the processes, alternative methods are always sharply more effective than classical ones. With the exception of SFE which does not allow extracting the totality of the active phenolic compounds, two of the other extraction methods were particularly promising. First, CPE afforded the most important yields in concentrated phenolic compounds (PC) (22.90±0.65% DW) also displaying the best activities (0.52±0.02 and 0.58±0.19 mg/mL for IC50 and AAC700, respectively). Secondly, PLE using an EtOH:water mixture 75:25 (v/v) allowed a good PC extraction (10.18±0.25% DW) with huge efficiency. Despite a lesser activity of the extracts (0.77±0.01 and 1.59±0.15 mg/mL for IC50 and AAC700, respectively) PLE is a green process and potentially complies European norms requirements for the prospective valorization of phenolic compounds from S. muticum in Brittany.

Advances in countercurrent chromatography for protein separations

Countercurrent chromatography (CCC) is a preparative purification technique working with biphasic liquid systems. One phase of the liquid system is selected to be the mobile phase, the other phase is the stationary phase, held still by centrifugal fields. Aqueous two-phase systems (ATPS) have demonstrated their use in biological purifications. This article reviews protein separations done by CCC using ATPS. The two types of CCC ‘columns’ – hydrostatic and hydrodynamic instruments – are presented. All commercially available CCC equipments are listed. The hydrostatic CCC columns have an interesting potential to purify proteins working with ATPS aqueous liquid phases. The ATPS properties are briefly summarized, giving the polyethylene glycol 1000/dipotassium phosphate/water ternary mass phase diagram, along with the full chemical compositions of the two aqueous phases of important mixtures of this ATPS. Most published protein purifications were performed in academic laboratories. The highest throughput listed is 1.65 g/h of pure lyzozyme, obtained using a 5.5 l hydrostatic CCC column.

A priori selection of the mobile and stationary phase in centrifugal partition chromatography and counter-current chromatography

The selection of the mobile and the stationary phase in support-free liquid-liquid chromatography (centrifugal partition chromatography and counter-current chromatography) is equivalent to a selection of a biphasic liquid system and its global composition. There is an immense number of choices of biphasic liquid systems. On one hand what makes this technique extremely versatile, on the other hand turns the selection of the appropriate system for a particular separation problem into a challenging and demanding task. In this work a systematic procedure for the selection of biphasic liquid systems for preparative scale separations is presented. The procedure is adaptable to the production scale requirements including production cost and safety. The experimental effort of different stages of the selection procedure is minimized by using a fully predictive method, the conductor-like screening model for real solvents (COSMO-RS). The COSMO-RS is used to assess properties relevant for the selection of a biphasic liquid system, such as the solute solubility and the partition coefficient.

Separation of a binary mixture by sequential centrifugal partition chromatography

Sequential centrifugal partition chromatography (sCPC) is a novel continuous cyclic liquid-liquid chromatographic separation technology. Each cycle of the process comprises two steps, which differ by the liquid phase used as mobile phase (upper or lower phase) and its flow direction. The feed is introduced continuously in the unit and two product streams are collected alternately, in each step of the cycle. In this work, the sCPC was modeled using the stage (cell) model. The model was used to simulate a separation of a model binary mixture consisting of pyrocatechol and hydroquinone. The solutes distribution constants, system hydrodynamics and mass transfer parameters were determined experimentally and implemented in the model. Furthermore, a parameter study (variation of the feed concentration and step times) was performed by experiments and simulation. A recently developed method was used to select the operating parameters of the sCPC unit.

Separation of natural products by countercurrent chromatography

Countercurrent Chromatography (CCC) provides the natural product chemist with a high-resolution separatory method, which is uniquely applicable to sensitive (unstable) compounds and which allows virtually quantitative recovery of the load sample. Different instruments use different means of retaining a stationary liquid phase. The solvent system (SS) can be chosen to optimize the separatory power and the number of systems available is limitless. Several examples are provided to illustrate the power of the method and to guide the chemist in choice of an appropriate SS.

Toroidal coil chromatography: the effect of scale-up and "g" field on stage efficiency

Selected test results have been taken from various publications and resolution and stage efficiency measured using an established model. All experiments used the same sample and, where possible, the same sample loading. The results show that stage mixing efficiencies have increased from 1.1% in 1998 to greater than 25% in the latest scaled-up version of a Toroidal coil chromatography (TCC) instrument working at 240 g.

Application of centrifugal precipitation chromatography and high-speed counter-current chromatography equipped with a spiral tubing support rotor for the isolation and partial characterization of carotenoid cleavage-like enzymes in Enteromorpha compressa (L.) Nees

Centrifugal precipitation chromatography and a high-speed counter-current chromatography system equipped with a spiral tubing support rotor (spHSCCC) were successfully applied for the identification and isolation of carotenoid cleavage-like enzymes from Enteromorpha compressa (L.) Nees. This is the first study separating active enzymes from a complex natural matrix by spHSCCC. The target enzymes were identified after fractionation of the proteins in an acetone Tris-buffer gradient by centrifugal precipitation chromatography. Also, an aqueous two-phase solvent system consisting of PEG 1000 and mono- and dibasic potassium phosphate was used for the isolation of the enzymes by spHSCCC. The purified fractions contained two proteins of 65 and 72 kDa, respectively. The enzymes could cleave β-carotene and β-apo-8'-carotenal to produce β-ionone.